Abstract: A chromatic dispersion compensator in a single-pass and a double-pass version is disclosed. In a single-pass version, the compensator has a diffractive grating for spatially separating an input optical signal into spatially spaced frequency components and a MEMS array of separate phase shifters, each for imparting an independent phase shift to a channel containing a range of the spatially spaced frequency components. In a double-pass version, a retroreflector is disposed to effect a double pass of the light beam through the grating and the phase shifters. The arrangement is effecting in reducing chromatic dispersion of the optical signal.

Abstract: Interleavers, based on a Michelson interferometer with a Gires-Tournois (GT) etalon in each arm, are becoming popular in the filtering of light in the fiber optics telecommunications industry. As the channel spacing becomes closer together, e.g. 50 GHz or 25 GHz, dispersion compensation becomes an important factor in the choice and design of a system. The present invention solves the problem of increased chromatic dispersion by utilizing multi-cavity Gires-Tournois (MCGT) etalons, wherein the dispersion from one MCGT is used to compensate or cancel the dispersion from the other MCGT. In an optimum design for a dual cavity GT etalon, the dispersion profile of the first MCGT will have a similar amplitude and frequency as the dispersion profile of the second MCGT, only shifted by half the period so that the positive slopes of one profile are aligned with the negative slopes of the other profile.

Abstract: The invention provides an optical switch having an input port for launching a beam of light into the optical switch, at least two output ports, each output port for selectively receiving a beam of light, an ATO element having optical power for providing an angle to offset transformation, and beam directing means for selectively directing a beam of light from the input port to a selected one of the at least two output ports along an optical path via the ATO element. The ATO element is a lens or a mirror.

Abstract: The present invention relates to an interferometer useful in the interleaving and de-interleaving of optical wavelength channels. Typically the invention comprises a beamsplitter and two resonators, e.g. GT etalons or ring resonators. The beamsplitter splits an input beam of light into a first sub-beam directed to follow a first path and a second sub-beam directed to follow a second path. The first resonator has a first effective cavity length and receives the first sub-beam. The second resonator has a second effective cavity length and receives the second sub-beam. The first path and the second path have an effective optical path difference approximately equal to one-half the first effective cavity length. In one embodiment, the front plates of the GT etalons each have a different reflectivity, and are selected to provide a desired spectral response.

Abstract: The invention provides a cylindrical polarization diversity circuit for narrowing the numerical aperture of an incoming beam of light in a direction perpendicular to the dispersion direction and without affecting the numerical aperture of the incoming beam of light in the direction of dispersion. A cylindrical lens is employed to provide an output beam having an elliptical cross-section. The output beam is collimated in one direction and diverging in a direction perpendicular thereto. A birefringent element having its walk-off direction oriented such that it coincides with the collimated beam direction separates the output beam into two orthogonally polarized sub-beams having an elliptical cross-section. The sub-beams are substantially non-overlapping. Advantageously, a halfwave plate is provided so as to make the polarization states of both sub-beams substantially parallel.

Abstract: In the invention, a stream (S) of solitons enters a Sagnac interferometer (6) with an offset semiconductor amplifier (A) and the amplifier is controlled by an optical synchronization signal (Y) that is amplitude-modulated at a frequency which is half a bit frequency of the stream, the offset of the amplifier in said interferometer and the parameters of said synchronization signal being given values such that two adjacent solitons of said train are transmitted with their optical phase relationship inverted. The invention finds an application in fiber optic telecommunications networks.

Abstract: To resynchronize input optical signals with different optical carrier frequencies f1, f2 a delayed optical signal is created by applying a variable time-delay to one of the signals. A combination signal is formed by coupling measurement optical signals respectively obtained from the delayed signal and from the other input signal. A mixed signal is formed by injecting the combination signal into a non-linear optical device. A filtered signal is formed from the mixed signal using a filter tuned to an optical frequency f3 equal to p.f1+q.f2, p and q being relative integers such that the frequency f3 is different to the frequencies f1 and f2 of the carrier waves. The variable time-delay is controlled in accordance with a control electrical signal representative of the average value of the intensity of the filtered signal. Applications include wavelength-division multiplex optical communication systems.

Abstract: The invention provides an optical switch having an input port for launching a beam of light into the optical switch, at least two output ports, each output port for selectively receiving a beam of light, an ATO element having optical power for providing an angle to offset transformation, and beam directing means for selectively directing a beam of light from the input port to a selected one of the at least two output ports along an optical path via the ATO element. The ATO element is a lens or a mirror.

Abstract: The invention provides an optical switch having a pair of opposed optical arrays, each optical array including a fixed mirror and a plurality of independently tiltable mirrors, at least one input port for launching a beam of light into the optical switch, said input port being disposed within a respective optical array, at least two output ports for selectively receiving a beam of light from an optical path between the at least one input port and a selected one of the at least two output ports, said at least two output ports being disposed within a respective opposed optical array, and an ATO element having optical power disposed between the pair of opposed optical arrays. The pair of opposed optical arrays is disposed in respective focal planes of the ATO element. Preferably, the ATO element has a focal length equal to a Rayleigh range of a beam of light incident thereon.

Abstract: In the area of wavelength division multiplexing (WDM), the present invention relates to a demultiplexer/multiplexer based on a diffraction grating, in which a beam of light is separated into two orthogonally polarized sub-beams prior to beam collimation. Due to the characteristics of the beam splitting crystal, parts of the sub-beams overlap resulting in portions of the sub-beams becoming improperly polarized. Too alleviate the errors cause thereby, an iris is placed over the diffraction grating to eliminate the portions of the light that have been polarized improperly.

Abstract: An optical device comprises a dispersion element, a reflector, and an angle-to-offset (ATO) element. The angle-to-offset (ATO) element has optical power. The dispersion element is positioned in or near a focal plane of the ATO element and adapted to separate an input wavelength division multiplexed (WDM) light beam received from an input port of the optical device into two or more channel light beams. The reflector is positioned in or near a focal plane of the ATO element and arranged to receive the channel light beams from the dispersion element via the ATO element. The reflector is designed to reflect at least one of the channel light beams toward a respective output port of the optical device. With this arrangement, the dispersion element, reflector and ATO element cooperate to optically demultiplex the input WDM light beam.

Abstract: A control system is designed to control an optical cross-connect having a switch core defined by first and second independently movable beam deflectors capable of selectively defining an optical path between a pair of ports of the optical cross-connect. An optical element having optical power is arranged in a propagation path of light beams between the first and second beam deflectors. The control system includes a pilot light source, an optical sensor associated with each beam deflector, and a feedback path. The a pilot light source inserts a pilot light into the switch core colinearly with live traffic. The optical sensor detects a predetermined geometric property of the pilot light emerging from the switch core. This predetermined geometric property is unambiguously associated with an angular position of the associated beam deflector. The feedback path actively controls a position of the associated beam deflector based on the detected geometric property.

Abstract: A device serving as an optical switch or attenuator is disclosed, based on the insertion of a halfwave plate in a collimated beam space between two lenses. All beams have first been aligned to a same polarization state by standard polarization diversity techniques. Moving the halfwave plate into or out of the beam incident thereon enables switching the beams direction based on polarization. Partial insertion of the waveplate attenuates the beam through rotation of polarization state for part of the beam. Preferably, polarizers are used to improve extinction ratio and wavelength flatness.

Abstract: A high capacity cross-connect in which a 3D switch core includes express paths that facilitate cascading of cross-connect blocks. A light beam propagates from an input waveguide 18 to a first MEMS mirror, which deflects the light beam to either an express optical path or a switching optical path. In the express optical path, the light beam propagates from the first MEMS mirror to a predetermined output waveguide, which is determined by the design of the switch core. In the switching optical path, the light beam propagates from the first MEMS mirror to a second MEMS mirror, which deflects the light beam to a selected one of a set of two or more output waveguides associated with the second MEMS mirror.

Abstract: The invention provides and optical switch having a first plurality of independently moveable deflectors with a first optical bypass for allowing the beam of light launched into an input port to pass therethrough, and a second plurality of independently moveable deflectors with a second optical bypass for allowing the beam of light to pass therethrough to any one of a plurality of output ports, said second plurality of independently moveable deflectors being disposed so as to receive the beam of light that passed through the first optical bypass, and wherein a switching is carried out by the first and second plurality of independently moveable deflectors. The optical elements are disposed about a common optical axis. Advantageously, the optical switch includes relay lenses for directing the light beam to the first optical bypass and for receiving it from the second optical bypass and directing it to the output ports.

Abstract: A multiplexing/demultiplexing optical circuit provides a demultiplexed output spectrum of channels having a flat amplitude response without sacrificing optical power. A phased array implementation and a diffraction grating implementation both rely on a first dispersion of the beam to be demultiplexed and subsequent division of the wavelengths into channels. Local inversion is induced within each channel of the dispersed wavelengths about a channel central wavelength. After the wavelengths are spatially inverted, they are once again provided to a dispersion element or array effectively nullifying the dispersion effects across the channel band to provide output channels having a substantially “flat-tops”, while providing good channel separation through global dispersion of all the wavelengths.

Abstract: The present invention relates to bi-directional circulators based on interleaver technology, e.g. birefringent crystal interleaver technology, that enables signals containing even number ITU channels to travel in one direction through the device, while signals containing odd number ITU channels travel in the opposite direction. Open and closed three and four port devices are disclosed, as well as several useful implementations of the three port device in combination with other optical components, which result in hybrid uni-directional and bi-directional devices.

Abstract: A conventional interleaver, based on a stack of waveplates, relies on the orientation and the birefringence of the waveplates to differentiate the polarizations of one set of channels from another, so that the one set of channels can be separated from the other. The present invention relates to a virtual waveplate that is used to replace a birefringent waveplate. A virtual waveplate imposes a phase delay between the extraordinary ray and the ordinary ray by separating one from the other and differentiating the actual path lengths taken thereby, before recombining them. An interleaver constructed with the virtual waveplates of the present invention can be substantially a-thermal and potentially chromatic dispersion free.

Abstract: An optical device for rerouting and modifying an optical signal that is capable of operating as a dynamic gain equalizer (DGE) and/or a configurable optical add/drop multiplexer (COADM) is disclosed. The optical design includes a front-end unit for providing a collimated beam of light, an element having optical power for providing collimating/focusing effects, a diffraction element for providing spatial dispersion, and modifying means which in a preferred embodiment includes one of a MEMS array and a liquid crystal array for reflecting and modifying at least a portion of a beam of light. The modifying means functions as an attenuator when the optical device operates as a DGE and as a switching array when the optical device operates as a COADM.

Abstract: Bi-directional wavelength interleaving optical isolators provide the ability to pass a first set of optical signals (e.g., ITU even channels) from a first port to a second port, while preventing a second set of optical signals from passing thereto. The bi-directional wavelength interleaving optical isolators also pass the second set of optical signals (e.g., ITU odd channels) from the second port to the first port, while preventing the first set of optical signals from passing thereto. Thus, the bi-directional wavelength interleaving optical isolator can provide bi-directional communications by passing a first set of signals in a first direction and a second set of signals in a second direction.